Clinical studies have established that deficiency of growth hormone (GH), also known as somatotropin in adults is associated with higher adiposity, reduced lean body mass, lower bone mineral density, and decreased quality of life ratings in a wide range of areas. Somatotropin deficiency is associated with decreased bone mineral content and density in patients with childhood or adult-onset disease. While delayed bone maturation and unachieved peak bone mass might explain reduced bone mineral density (BMD) in patients afflicted with GH deficiency as children, the pathophysiology of low BMD in patients with adult-onset somatotropin deficiency is less clear. Recent research suggests that chronic somatotropin therapy can reverse some of the bony changes associated with adult-onset somatotropin deficiency. Unfortunately, the studies conducted thus far have lacked sufficient control measures to be regarded as "definitive." The aim of the present study is to investigate, in a randomized placebo-controlled design, the effect of chronic somatotropin treatment on BMD in patients diagnosed with adult-onset somatotropin deficiency. The primary objective is to test the hypothesis that patients with adult-onset growth hormone deficiency who are treated with somatotropin will have a greater bone mineral density of the spine and the femoral neck, than those who are treated with placebo at the end of 2 years of treatment. The secondary objectives of the study are as follows: 1) to test the hypothesis that patients with adult-onset growth hormone deficiency who are treated with somatotropin will demonstrate increased bone formation and decreased bone breakdown, as assessed by serum and urinary markers, than those treated with placebo. 2) to assess adverse events associated with 2 years of somatotropin treatment in patients with adult-onset growth hormone deficiency. 3) to collect data on a new health-related quality of life questionnaire for Somatotropin Deficiency Syndrome (SDS). This will be a multi-center, parallel, double-blind, placebo-controlled study involving 72 patients diagnosed with somatotropin deficiency syndrome. Approximately 9-10 patients will be recruited for the study at our institution. Patients fulfilling the entry criteria will be randomized at Visit 2 to either somatotropin therapy or placebo. Clinical assessment of randomized patients will take place at 1,2,3,4,6,7,12,18, and 24 months after treatment is initiated. Clinical assessment will consist of BMD measurements using Dual Energy X-ray Absorptiometry (DEXA) and laboratory tests (n-telopeptide, creatinine, and alkaline phosphatase) for bone turnover. BMD assessment and the latter laboratory tests will be done before treatment and at 6,12,18 and 24 months. Patients who are nutritionally deficient, based on a nutritional assessment at Visit 2, will be given supplements for optimal calcium and vitamin D levels.